Sleep apnea is a sleep-related breathing disorder that is thought to affect between one and ten percent (1-10%) of the adult population. Recent epidemiologic data indicate that two percent (2%) of women and four percent (4%) of men between the ages of thirty (30) and sixty (60) years old meet the minimum diagnostic criteria for sleep apnea syndrome, representing more than ten million individuals in the United States. It is a disorder with significant morbidity and mortality, contributing to increased risk of hypertension, cardiac arrhythmias, stroke, and cardiovascular death. Another common sleep-related breathing disorder is snoring, which may be associated with or independent of sleep apnea.
One of the main reasons for sleep disturbance is relaxation of the tongue and pharyngeal walls to varying degrees during the several stages of sleep. When fully awake, these tissues have normal tone as air passes in and out of the lungs during respiration. However, during sleep, the musculature supporting these tissues relaxes. As air is inspired, the tongue and walls of the pharynx collapse, causing snoring or more seriously, causing partial or complete obstruction of the airway.
Obstructive sleep apnea occurs due to a collapse of soft tissue within the upper airway during sleep. The ongoing force of inspiration serves to generate increasingly negative pressure within the pharynx, causing further collapse. The lack of respiration results in inadequate blood oxygenation, and rising carbon dioxide levels. The cardiovascular response produces an increase in blood pressure and pulse. Cardiac arrhythmias often occur. The carbon dioxide increase and oxygen desaturation triggers a transition to a lighter sleep stage, usually without wakefulness. This transition brings a return to tonicity of the muscles of the upper airway, allowing normal breathing to resume. The person then returns to deeper stages of sleep and the process is repeated. The disease is quantified in terms of respiratory disturbances per hour. Mild disease begins at ten per hour, and it is not uncommon to find patients with indices of about one hundred or more.
Not surprisingly, sleep is extremely fragmented and of poor quality in persons suffering from sleep apnea. As a result, such persons typically feel tired upon wakening and may fall asleep at inappropriate times during the day. All aspects of quality of life, from physical and emotional health, to social functioning are impaired by obstructive sleep apnea.
Continuous Positive Airway Pressure (“CPAP”) is a popular non-surgical treatment for patients suffering from sleep apnea. CPAP is administered by means of a mechanical unit that delivers pressurized room air to the nasal passage, or airway, through a nose mask that is worn by the patient during sleep. Pressurized air enters from the CPAP unit through the nose when a person is sleeping, and opens the airway from the inside almost as if the air were an internal splint. The correct pressure for the individual is determined in a sleep laboratory. If the nasal airway admits the flow of air, CPAP has in many cases offered immediate relief. Unfortunately however, compliance with, and long-term acceptance of this treatment are generally poor. Studies have shown that between twenty and fifty percent (20-50%) of patients fail to use nasal CPAP as prescribed. Problems associated with CPAP include excessive dryness of the mouth and throat, mucous congestion, sinusitis, and rhinorrhea. Breathing against positive air pressure is also discomforting to many patients.
Other non-surgical treatments for sleep apnea include the use of tongue retaining devices and other oral appliances that hold and/or pull the tongue or jaw in a forward position to open the airway by reducing collapse of the soft palate and/or tongue. These devices also suffer from poor compliance rates, and are usually associated with degenerative changes in the temporomandibular joint.
Surgical procedures have also been proposed and/or practiced for the treatment of moderate to severe sleep apnea. Uvulopalatopharyngoplasty (“UPPP”) is a surgical procedure used to treat obstructive sleep apnea. In UPPP, any remaining tonsillar tissue and a portion of the soft palate is removed. The procedure increases the width of the airway at the throat opening. However, UPPP does not address apnea caused by obstructions deeper in the throat and airway, for example, apnea resulting from collapse of tissue near the base of tongue or in the oropharyngeal region of the airway.
LAUP, or Laser-Assisted Uvulopalatoplasty, is a modification of the above-mentioned technique, but has not proven particularly useful for sleep apnea. These surgical techniques are extremely invasive, requiring general anesthesia, and a prolonged, painful recovery.
Radio frequency tissue ablation (“RFTA”) has also been suggested for shrinking the soft palate, uvula and reducing tongue volume in the treatment of snoring and obstructive sleep apnea. Somnoplasty utilizes a radiofrequency tool that generates heat to create coagulative lesions at specific locations within the upper airway. The lesions created by the procedure are naturally resorbed in approximately three to eight weeks, reducing excess tissue volume and increasing the airway opening. Like UPPP and LAUP, more than one session is typically required and it does not address sleep apnea resulting from tissues deeper in the throat than the upper airway.
Another area of surgical interest lies in techniques designed to pull the tongue anteriorly. For example, a tongue suspension procedure has been suggested in which the tongue is pulled forward, thereby keeping the tongue from falling into the airway during sleep. The system utilizes a bone screw inserted into the mandible. The screw attaches to a non-absorbable suture which travels the length of the tongue and back. Similarly, the hyoid bone can be drawn anteriorly with two distinct screws, also attached to the mandible.
Techniques have also been developed for treating, specifically, the condition of snoring. For example, U.S. Pat. No. 6,250,307 to Conrad et al. discloses a method for treating snoring of a patient that includes embedding a fibrosis-inducing implant into a soft palate of a patient in order to alter a dynamic response of a soft palate to airflow.
Concepts relating to implants in the pharyngeal area have been described in German publication DE 19,920,114 to Fege, published Nov. 9, 2000, which discloses transverse implant bands attached at one end to the cervical vertebra via surgical slits through the tongue, tonsils, and pharyngeal tissue. Other pharyngeal implants have been described in U.S. Publication No. 2003/0149488 to Metzger et al., now U.S. Pat. No. 7,017,582.
These conventional devices and treatments continue to suffer poor cure rates. The failures may lie in their inability to maintain patency in the retropalatal region and retroglossal region (the caudal margin of the soft palate to the base of the epiglottis). The poor success rates combined with high morbidity, contribute to an ongoing need for more effective treatments for sleep apnea and/or snoring.